Lubrication Analysis for a Line Contact Covering from Boundary Lubrication to Hydrodynamic Lubrication: Part I-Micro Contact Results

Abstract

The paper presents an analysis for a line contact where physical adsorbed layer boundary lubrication or hydrodynamic lubrication may occur, considering the boundary film dynamic and noncontinuum effects, the contact surface thermo-elastic deformation, the surface pressure effect, the contact surface shear stress effect on the contact surface deformation and the contact surface elastoplastic deformation. Exemplary calculations were first made for a micro contact. The obtained results show that in a micro line contact the contact surface thermo-elastic deformation has a negligible influence on the central film thickness for modest sliding speeds and loads, however it can yield a more than 10% reduction of the contact load-carrying capacity for very high sliding speeds and heavy loads due to the contact severe frictional heating. When the contact is in boundary lubrication, for a given load, a non-continuum boundary film model gives a considerably higher central film thickness than a continuum lubricating film model whenever the contact is in elastic, elastoplastic or fully plastic deformation, and a strong boundary film–contact interaction gives a greatly increased central film thickness and a much more insensitive central film thickness-load variation than a weak boundary film–contact interaction, which sustains a considerably high central film thickness in the contact even for heavy loads. The boundary film compressibility caused by the boundary film–contact interaction reduces the contact load-carrying capacity. The surface pressure and the contact surface shear stress were analyzed to have no influence on the total contact surface deformation and the central film thickness.